JP6200323B2 - Non-aqueous ink, method for producing the same, and pigment dispersant - Google Patents

Description

  The present invention relates to a non-aqueous ink, particularly a non-aqueous ink suitable for use in an ink jet recording apparatus, a method for producing the same, and a pigment dispersant.

  Inkjet recording is a method in which high-fluidity inkjet ink is ejected from fine head nozzles as ink particles, and an image is recorded on a recording medium placed opposite to the nozzle, enabling high-speed printing with low noise. Therefore, it has been spreading rapidly in recent years. As an ink used in such an ink jet recording system, a so-called non-aqueous ink in which a color material is finely dispersed in a water-insoluble solvent is known.

  In recent years, it has been desired to reduce the power consumption of devices such as printers as much as possible from the viewpoint of resource environment and energy saving, and the demand for power saving is increasing more and more in ink-jet printing in order to save power.

In an ink jet recording apparatus, pressure is applied to an ink chamber provided in an ink jet head, and ink in the ink chamber is ejected from a nozzle. However, since the viscosity of the ink increases in a low temperature environment, a desired amount of ink is ejected. For this reason, it is necessary to increase the drive voltage of the ink jet head, which increases power consumption. Further, if discharge is performed with a high driving voltage, satellites are likely to be generated. Satellites adhere to the recording medium and reduce the print quality. Therefore, conventionally, in a low temperature environment where satellites are likely to be generated, recording is started after performing a so-called warm-up operation for heating the inkjet head in order to ensure print quality. This warm-up operation also causes an increase in power consumption.
From the above, in order to suppress power consumption, it is conceivable to reduce the viscosity of ink in a low temperature environment. However, it is extremely effective to reduce the viscosity of ink as a means for that purpose. Although it is possible to reduce the viscosity of the ink by reducing the amount of the color material and the amount of powder in the ink, there is a problem that the print density is lowered and the image quality is lowered.

  In order to solve the above problems, for example, Patent Document 1 discloses a primary and / or 2 in one molecule chemically reacted to a dispersant by reacting with a pigment, a dispersant, and a reactive functional group of the dispersant. An ink using a colorant in which a water-soluble resin containing two or more primary amino groups is combined has been proposed. This ink has high storage stability, pigment dispersibility, and ejection stability that does not cause clogging at the nozzle portion. However, with the colorant described in Patent Document 1, it is necessary to increase the amount of the dispersant in order to stabilize the ink in a low temperature environment, and the viscosity cannot be lowered to such an extent that the satellite is suppressed. .

By the way, it is possible to reduce the viscosity of the ink by using a hydrocarbon-based high boiling point and low-viscosity nonpolar solvent (hereinafter simply referred to as a hydrocarbon-based nonpolar solvent). The use of a hydrocarbon-based non-polar solvent as the ink solvent changes the polarity of the ink solvent and may deteriorate the pigment dispersion stability. This is considered to be solved by changing the composition of the dispersant. . Patent Document 2 proposes a non-aqueous pigment ink containing water-insoluble resin-dispersed fine particles having pigment dispersing ability.
However, the water-insoluble resin-dispersed fine particles described in Patent Document 2 have a functional group (urethane group) that adsorbs to the pigment inside the hydrocarbon-based nonpolar solvent and has an affinity for the hydrocarbon-based nonpolar solvent. In this case, the water-insoluble resin-dispersed fine particles are difficult to adsorb on the pigment, and a sufficient amount of pigment dispersibility cannot be ensured with a small amount. For this reason, it is necessary to preliminarily prescribe a large amount of water-insoluble resin-dispersed fine particles for the pigment, which causes a problem that the ink viscosity increases. On the other hand, the pigment dispersibility needs to have good affinity between the hydrocarbon-based nonpolar solvent and the pigment. If the affinity is too high, the pigment disperses when the hydrocarbon-based nonpolar solvent penetrates into the recording medium. However, there is a tendency to be easily pulled into the recording medium. As a result, the print density is lowered and the show-through tends to occur.

JP 2008-19333 A JP 2010-1452 A

  In order to solve the above problems, the present applicant is a non-aqueous pigment ink containing a pigment, a non-aqueous solvent, a water-insoluble resin, and a water-soluble resin, and the water-insoluble resin has at least carbon number. An acrylic resin comprising a copolymer of a monomer mixture containing an alkyl (meth) acrylate (A) having 8 to 18 alkyl groups and a monomer (B) having a β-diketone group or β-keto ester group. A non-aqueous pigment ink was proposed (Japanese Patent Application No. 2012-151614). Generally, a pigment dispersant is in an equilibrium state by repeating adsorption and desorption on the pigment surface to stabilize the ink. However, in the non-aqueous pigment ink, a water-insoluble resin as a pigment dispersant is added to the pigment surface. The ink can be stabilized. As a result, power saving, satellite suppression and printing density improvement can be achieved, while low temperature aptitude and pigment dispersion stability can be ensured, and at the same time, show-through can be suppressed and high printing density can be realized. Can do.

  However, the above-mentioned non-aqueous pigment ink has a problem that it emits an unpleasant amine odor when a water-soluble resin containing an amino group such as polyethyleneimine is used as the water-soluble resin, leaving room for improvement.

  The present invention has been made in view of the above-described conventional problems, and its problem is a non-aqueous ink that can reduce amine odor while maintaining power saving, satellite suppression, and printing density improvement, and a method for producing the same. And providing a pigment dispersant.

The present invention for solving the above problems is as follows.
(1) A non-aqueous ink containing at least a pigment, a pigment dispersant, and a non-aqueous solvent,
A non-aqueous ink in which the pigment dispersant comprises a copolymer containing at least a monomer (A) having a β-dicarbonyl group and a water-soluble resin (B) having an amino group as constituent components.

(2) The non-aqueous ink according to (1), wherein the copolymer further contains an alkyl (meth) acrylate (C) having an alkyl group having 8 to 18 carbon atoms as a constituent component.

(3) A pigment dispersant comprising a copolymer containing at least a monomer (A) having a β-dicarbonyl group and a water-soluble resin (B) having an amino group as constituent components.

(4) A method for producing a non-aqueous ink comprising at least a pigment, a pigment dispersant, and a non-aqueous solvent,
A polymer containing at least a monomer (A) having a β-dicarbonyl group as a constituent component is synthesized, and then a copolymer containing at least the polymer and a water-soluble resin (B) having an amino group as constituent components is synthesized. And a step of preparing a pigment dispersant;
A method for producing a non-aqueous ink comprising a step of mixing and dispersing at least the pigment dispersant, a pigment, and a non-aqueous solvent.

  ADVANTAGE OF THE INVENTION According to this invention, the non-aqueous ink which can reduce an amine odor, and its manufacturing method, and a pigment dispersant can be provided, maintaining a power saving, satellite suppression, and a printing density improvement.

<Non-aqueous ink>
The non-aqueous ink of the present invention is a non-aqueous ink containing at least a pigment, a pigment dispersant, and a non-aqueous solvent, wherein the pigment dispersant has a monomer (A) having a β-dicarbonyl group (hereinafter, referred to as “non-aqueous ink”). It may be simply referred to as “monomer (A)”) and a water-soluble resin (B) having an amino group as a constituent component.
The non-aqueous ink of the present invention has the effects of the non-aqueous pigment ink proposed by the present applicant (Japanese Patent Application No. 2012-151614) (power saving, satellite suppression and printing density improvement, low temperature suitability and pigment dispersion stability, The amine odor is reduced while maintaining the suppression of show-through.
Hereinafter, each component of the non-aqueous ink of the present invention will be described in detail.

[Pigment]
The non-aqueous ink of the present invention may have any color, and therefore, as the pigment, organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, dyed lake pigments, and inorganic pigments can be used. Examples of the azo pigments include soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments. Examples of phthalocyanine pigments include metal phthalocyanine pigments and metal-free phthalocyanine pigments. Polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxysazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments. And diketopyrrolopyrrole (DPP). Representative examples of inorganic pigments include carbon black and titanium oxide. These pigments may be used alone or in combination of two or more.

  The content of the pigment in the non-aqueous ink of the present invention is usually 0.01 to 20% by mass, preferably 1 to 15% by mass from the viewpoint of printing density and ink viscosity, and 5 to 10% by mass. More preferably it is.

  The average particle size of the pigment in the ink is preferably about 500 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less. On the other hand, the average particle diameter is preferably about 50 nm or more in order to prevent the print-through of the printed matter. Here, the average particle diameter of the pigment is a volume-based value measured by a dynamic light scattering particle size distribution measuring device LB-500 manufactured by Horiba, Ltd.

[Non-aqueous solvent]
As the non-aqueous solvent, any of a non-polar organic solvent and a polar organic solvent can be used. These may be used alone or in combination of two or more as long as they form a single phase. From the viewpoint of lowering the viscosity, it is preferable to use a nonpolar organic solvent.
The content of the nonpolar organic solvent is preferably 20% by mass or more, more preferably 40% by mass or more, and further preferably 50% by mass or more with respect to the total mass of the ink solvent. When the content of the hydrocarbon-based nonpolar solvent is 20% by mass or more based on the total amount of the solvent, the viscosity can be sufficiently lowered.

  When the content of the nonpolar organic solvent is 50% by mass or more with respect to the total mass of the ink solvent, it is possible to obtain the effect of further reducing the viscosity of the ink and further improving the storage stability. When the content of the nonpolar organic solvent is 50% by mass or more with respect to the total mass of the ink solvent, the water-soluble resin hardly collects in the ink solvent and gathers in the vicinity of the pigment and is firmly adsorbed on the surface of the pigment. To come. For this reason, not only can the viscosity of the solvent itself be lowered, but also the effect of lowering the viscosity can be obtained by reducing the amount of free resin in the solvent, and the dispersion stability of the pigment can be further improved. It is estimated that

  Preferable examples of the nonpolar organic solvent include petroleum hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents. Examples of the aliphatic hydrocarbon solvent and alicyclic hydrocarbon solvent include paraffinic, isoparaffinic, and naphthenic solvents. For example, what is sold with the following brand names is mentioned. Teclean N-16, Teclean N-20, Teclean N-22, Naphthezol L, Naphthezol M, Naphthezol H, No. 0 Solvent L, No. 0 Solvent M, No. 0 Solvent H, Isosol 300, Isosol 400, AF Solvent No. 4, AF Solvent No. 5, AF Solvent No. 6, and AF Solvent No. 7 (all manufactured by JX Nippon Oil & Energy Corporation); Isopar G, Isopar H, Isopar L, Isopar M, Exol D40, Exol D80, Exol D100, Exol D130 and Exol D140 (both manufactured by TonenGeneral Sekiyu KK). Examples of the aromatic hydrocarbon solvent include grade alkene L, grade alkene 200P (all manufactured by JX Nippon Oil & Energy Corporation), Solvesso 200 (manufactured by TonenGeneral Sekiyu KK), and the like.

  Preferable examples of the polar organic solvent include ester solvents, higher alcohol solvents, higher fatty acid solvents, and the like. For example, methyl laurate, isopropyl laurate, isopropyl myristate, isopropyl palmitate, isostearyl palmitate, methyl oleate, ethyl oleate, isopropyl oleate, butyl oleate, methyl linoleate, isobutyl linoleate, ethyl linoleate , Isopropyl isostearate, soybean oil methyl, soybean oil isobutyl, tall oil methyl, tall oil isobutyl, diisopropyl adipate, diisopropyl sebacate, diethyl sebacate, propylene glycol monocaprate, trimethylolpropane tri-2-ethylhexanoate, tri Ester solvent having 14 or more carbon atoms in one molecule such as glyceryl 2-ethylhexanoate; isomyristyl alcohol, isopalmityl alcohol, isostear Higher alcohol solvents with 8 or more carbon atoms in one molecule such as alcohol, oleyl alcohol, etc .; carbon in one molecule such as isononanoic acid, isomyristic acid, hexadecanoic acid, isopalmitic acid, oleic acid, isostearic acid And higher fatty acid solvents having a number of 9 or more.

[Pigment dispersant]
In the present invention, the pigment dispersant is composed of a copolymer containing at least a monomer (A) having a β-dicarbonyl group and a water-soluble resin (B) having an amino group as constituent components. By using a β-dicarbonyl group and an amino group as a copolymer, the remaining as a water-soluble resin having an amino group can be suppressed, and the amine odor can be suppressed. The reason will be described later.
Below, each structural component which comprises the said copolymer is demonstrated.

(Monomer (A) having β-dicarbonyl group)
Examples of the monomer (A) having a β-dicarbonyl group include monomers containing a β-diketone group or a β-keto acid ester group, a β-ketoamide, and a cyanoacetate. In the present invention, a copolymer is obtained by using at least the monomer (A) and the water-soluble resin (B) having an amino group. Both of them are a carbonyl group of the monomer (A) and an amino group. It is considered that a bond is formed by a reaction with an amino group of a water-soluble resin having a salt.
The pigment dispersant containing the monomer (A) has high adsorptivity to the pigment, whereby the pigment dispersibility is improved, the viscosity of the ink is lowered, and the low temperature suitability can be improved. In addition, because it has low viscosity and excellent low-temperature suitability, it contributes to electrostatic aggregation and fixing of ink when landing on a recording medium, and as a result, it can improve printing density and achieve back-through suppression. it can. In addition, water-soluble resin (B) is inherently unsuitable for non-polar organic solvents, but reacting with monomer (A) makes it easier to become compatible with non-polar organic solvents and improves wettability (dispersibility) with pigments. To do.

  Preferred examples of the monomer (A) include (meth) acrylates and (meth) acrylamides containing a β-diketone group or β-keto acid ester group in the ester chain. More specifically, acetoacetoxyalkyl (meth) acrylates such as acetoacetoxyethyl (meth) acrylate, acetoacetoxyalkyl (meth) acrylamides such as hexadione (meth) acrylate, acetoacetoxyethyl (meth) acrylamide, and the like can be mentioned. These may be used alone or in combination of two or more.

(Water-soluble resin having amino group (B))
Examples of the water-soluble resin (B) having an amino group include basic polymer electrolytes such as polyethyleneimine (PEI), polyvinylamine, and polyvinylpyridine, or derivatives thereof, and in particular, the weight average molecular weight is 200 to 200. 2000 polyethyleneimines can be preferably used.

  If the weight average molecular weight of the polyethyleneimine is less than 200, the effect of increasing the density with respect to plain paper may be reduced, and if it exceeds 2000, the ink repellency of the nozzle plate may be deteriorated. The weight average molecular weight of the polyethyleneimine is more preferably 300 to 1800, which has a large effect of increasing the concentration and has good nozzle plate ink repellency.

  As the polyethyleneimine, commercially available products can be used. For example, Epomin SP-006, Epomin SP-012, Epomin SP-018, Epomin SP-200 manufactured by Nippon Shokubai Co., Ltd. Lupasol FG, Lupasol manufactured by BASF Corporation G20 Waterfree, Lupasol PR8515, etc. can be mentioned preferably.

(Alkyl (meth) acrylate (C))
The copolymer which is a pigment dispersant according to the present invention preferably further contains an alkyl (meth) acrylate (C) having an alkyl group having 8 to 18 carbon atoms as a constituent component. Alkyl (meth) acrylate (C) is highly compatible with the non-aqueous solvent hydrocarbon-based nonpolar solvent by containing an alkyl group having 8 to 18 carbon atoms, thereby being dissolved in the non-aqueous solvent, On the other hand, when the copolymer is used, the viscosity of the ink can be lowered by the β-dicarbonyl group of the monomer (A), and the low-temperature suitability can be further improved. In addition, by suppressing the increase in viscosity, it contributes to electrostatic aggregation and fixing of the ink when the ink lands on the recording medium. As a result, the printing density is improved and the back-through is suppressed. be able to.

  If the alkyl group has 19 or more carbon atoms in the alkyl (meth) acrylate (C), the water-insoluble resin tends to solidify at low temperatures and the low-temperature suitability may deteriorate. On the other hand, when the number of carbon atoms is 7 or less, the compatibility with the hydrocarbon-based nonpolar solvent is lowered, and the pigment cannot be stably dispersed, so that the storage stability is deteriorated and the viscosity of the ink is high. It may become. Further, in a low temperature environment, the ink viscosity is further increased, and the low temperature aptitude is deteriorated. The number of carbon atoms of the alkyl group is more preferably 12-18.

  The alkyl group having 8 to 18 carbon atoms may be linear or branched. Specifically, an octyl group, a nonyl group, a decyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, and the like may be mentioned, and these may include a plurality of types. .

  Examples of the β-diketone group constituting the functional group include acetoacetyl group and propionacetyl group as preferred examples. Examples of the β-keto acid ester group include acetoacetoxy group and propionacetoxy group as preferred examples. Can be mentioned.

The molecular weight (weight average molecular weight) of the alkyl (meth) acrylate (C) is not particularly limited, but when used as an inkjet ink, it is preferably about 5000 to 50000 from the viewpoint of ink ejection properties, and is preferably 10,000 to 10,000. More preferably, it is about 30000.
The glass transition temperature (Tg) of the alkyl (meth) acrylate (C) is preferably not higher than normal temperature, and more preferably 0 ° C. or lower. Thereby, when the ink is fixed on the recording medium, the film formation can be promoted at room temperature.

The mass ratio ((A) :( B)) of the monomer (A) having a β-dicarbonyl group and the water-soluble resin (B) having an amino group is preferably 1: 2 to 20: 1. : 1 to 15: 1 is more preferable, and 2: 1 to 10: 1 is still more preferable.
Moreover, when using alkyl (meth) acrylate (C), it is preferable that alkyl (meth) acrylate (C) is 10-400 mass parts with respect to 100 mass parts of monomers (A), and 50-350 mass parts. It is more preferable that it is 90 to 300 parts by mass.

  Each of the above components can be easily polymerized by known radical copolymerization. The reaction system is preferably carried out by solution polymerization or dispersion polymerization. In this case, in order to make the molecular weight of the acrylic resin after polymerization within the above preferred range, it is effective to use a chain transfer agent in combination during the polymerization. Examples of the chain transfer agent include thiols such as n-butyl mercaptan, lauryl mercaptan, stearyl mercaptan, and cyclohexyl mercaptan.

  Examples of the polymerization initiator include azo compounds such as AIBN (azobisisobutyronitrile), t-butylperoxybenzoate, t-butylperoxy-2-ethylhexanoate (Perbutyl O, manufactured by NOF Corporation), etc. Known thermal polymerization initiators such as peroxides can be used. In addition, a photopolymerization initiator that generates radicals upon irradiation with active energy rays can be used. As a polymerization solvent used for solution polymerization, for example, a petroleum solvent (aroma free (AF) system) or the like can be used. As the polymerization solvent, it is preferable to select one or more kinds of solvents (which will be described later) that can be used as they are as non-aqueous solvents for ink. In the polymerization reaction, other commonly used polymerization inhibitors, polymerization accelerators, dispersants and the like can also be added to the reaction system.

(Content of each component)
The content of the pigment dispersant with respect to the total amount of the ink is preferably 0.1% by mass or more, and more preferably 1% by mass or more from the viewpoint of securing the dispersibility of the pigment. On the other hand, if the content of the pigment dispersant is too high, not only the viscosity of the ink is increased, but also the storage stability in a high temperature environment may be deteriorated. It is more preferable that the amount is not more than mass%. That is, the content of the pigment dispersant with respect to the total amount of the ink is more preferably 1 to 10% by mass, and further preferably 2 to 8% by mass.

  The content of the pigment dispersant with respect to the pigment is preferably 0.1 to 1.0 in terms of mass ratio to the pigment from the viewpoint of ensuring storage stability. When the content of the pigment dispersant with respect to the pigment is too small as less than 0.1 by mass ratio with respect to the pigment, or when it is too large with more than 1.0, it may be difficult to ensure storage stability.

  The non-aqueous ink of the present invention may contain conventional additives in addition to the above components. Additives include surfactants such as anionic, cationic, amphoteric or nonionic surfactants, antioxidants such as dibutylhydroxytoluene, propyl gallate, tocopherol, butylhydroxyanisole, and nordihydroguaiare. And tic acid.

  The viscosity of the non-aqueous ink of the present invention is preferably 5 to 30 mPa · s at 23 ° C., although the suitability range varies depending on the nozzle diameter of the ejection head, the ejection environment, etc. in the case of an inkjet recording system. It is more preferably 5 to 15 mPa · s, and about 10 mPa · s is suitable for an inkjet recording apparatus. Here, the viscosity represents a value at 10 Pa when the shear stress is increased from 0 Pa at a rate of 0.1 Pa / s at 23 ° C.

<Method for producing non-aqueous ink>
The above non-aqueous ink of the present invention can be produced by the non-aqueous ink production method of the present invention. That is, the method for producing a non-aqueous ink of the present invention is a method for producing a non-aqueous ink containing at least a pigment, a pigment dispersant, and a non-aqueous solvent, and includes a monomer (A) having a β-dicarbonyl group. Synthesizing a polymer containing at least as a constituent component, then synthesizing a copolymer containing at least the polymer and a water-soluble resin (B) having an amino group as a constituent component, and preparing a pigment dispersant; And a step of mixing and dispersing at least a pigment dispersant, a pigment, and a non-aqueous solvent.

In the method for producing a non-aqueous ink according to the present invention, a pigment dispersant is prepared in advance, and then mixed and dispersed with other components of the non-aqueous ink. By doing so, the amine odor can be reduced. Can be planned. The reason is guessed as follows.
For example, when the pigment, the monomer (A) having a β-dicarbonyl group, and the water-soluble resin (B) are blended at the time of dispersion, the adsorption ability for the pigment is higher than that of the water-soluble resin (B). Therefore, it is considered that the monomer (A) is preferentially adsorbed on the pigment and a large amount of unreacted water-soluble resin (B) remains. The cause of the amine odor is presumed to be the unreacted water-soluble resin.
On the other hand, when the monomer (A) and the water-soluble resin (B) are reacted (copolymerized) in advance, the monomer (A) efficiently reacts with the water-soluble resin (B). The remaining amount of the functional resin (B) is small. Therefore, even when the ink is mixed and dispersed with the pigment in this state, the remaining amount of the unreacted water-soluble resin (B) is small, and it is presumed that the amine odor is reduced as compared with the above case. In the present invention, not the monomer (A), but a polymer containing at least the monomer (A) as a constituent component is used, but the above-mentioned monomer (A) is included as a constituent component of the polymer. The argument is valid.

In the production method of the present invention, the step of preparing a pigment dispersant comprises synthesizing a polymer containing at least a monomer (A) having a β-dicarbonyl group, and then a water-soluble resin (B) having the polymer and an amino group. ) And at least a copolymer to synthesize a copolymer.
As described above, the copolymer preferably further includes an alkyl (meth) acrylate (C) having an alkyl group having 8 to 18 carbon atoms as a constituent component. In this step, the amount of each component used is as described in the non-aqueous ink of the present invention described above.
Further, the copolymerization conditions are as described in the non-aqueous ink of the present invention described above, and therefore specific reaction conditions will be described here. A suitable reaction flow is as follows.
(1) Heat the non-aqueous solvent in a predetermined container to 50 to 150 ° C.
(2) Raw material monomers (monomer (A) and optionally monomers such as alkyl (meth) acrylate (C)) are added to the non-aqueous solvent over 1 to 5 hours.
(3) Further, after 1 to 5 hours, dilute with a non-aqueous solvent.
(4) Further, after 1 to 5 hours, the water-soluble resin (B) is added and stirred for 1 to 3 hours.
A colorless and transparent copolymer can be obtained as described above.
In addition, conditions, such as temperature and time, can be suitably set according to the kind, compounding ratio, etc. of a monomer or water-soluble resin.

  Next, using the pigment dispersant obtained as described above, a non-aqueous ink is obtained through a step of mixing and dispersing at least the pigment dispersant, the pigment, and the non-aqueous solvent. Specifically, each component is mixed so as to be in the range of “content of each component” shown in the above description of the non-aqueous ink of the present invention, and then dispersed to obtain a non-aqueous ink.

<Pigment dispersant>
The pigment dispersant of the present invention is characterized by comprising a copolymer containing at least a monomer (A) having a β-dicarbonyl group and a water-soluble resin (B) having an amino group as constituent components.
The pigment dispersant of the present invention corresponds to the pigment dispersant of the non-aqueous ink of the present invention described above. Accordingly, the description and preferred examples of each component and the production method are valid as they are as the description of the pigment dispersant of the present invention, and thus the detailed description is omitted.
The pigment dispersant of the present invention can exhibit excellent dispersibility with respect to the pigment in a non-aqueous solvent. In addition, amine odor is suppressed.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[Examples 1-6, Comparative Examples 1-5]
(Synthesis of resins 1 to 7)
In a four-necked flask, Isopar G (naphthenic solvent; manufactured by TonenGeneral Sekiyu KK) was charged, and the temperature was raised to 110 ° C. with aeration and stirring of nitrogen gas. Subsequently, each monomer mixture (except for the water-soluble resin (B)) having the composition shown in Table 1 was dropped over 3 hours while maintaining the temperature at 110 ° C. Thereafter, after 1 hour and 2 hours while maintaining at 110 ° C., the polymer was diluted with Isopar G to obtain a polymer. Subsequently, the water-soluble resin (B) of the number of parts shown in Table 1 was mixed and stirred for 3 hours to obtain colorless and transparent resins (copolymers) 1 to 7 having a nonvolatile content of 50%. The obtained resin solution had a weight average molecular weight (GPC method, standard polystyrene conversion) of 8200-12500.

(Preparation of non-aqueous ink)
In the proportions shown in Table 2, pigment (carbon black, MA8 manufactured by Mitsubishi Chemical Corporation), resins 1 to 7 obtained as described above as a pigment dispersant, polyethyleneimine (Epomin SP- manufactured by Nippon Shokubai Co., Ltd.) 012), Isopar G (naphthenic solvent; manufactured by TonenGeneral Sekiyu K.K.) was mixed as a solvent during dispersion, and the resulting prepared liquid was sufficiently dispersed with a bead mill to prepare a pigment dispersion. Then, after adding ISOPAR G as a viscosity adjusting solvent and diluting, the diluted solution is centrifuged, filtered through a 3 μm membrane filter to remove dust and coarse particles, and non-aqueous ink (hereinafter simply referred to as “ink”). ").

(Evaluation)
The following evaluation was performed using each of the obtained non-aqueous inks.
(1) Odor About 20 ml of ink was placed in a 50 ml glass bottle and sealed with a cap. After storing this at 23 ° C. for 1 week, the cap was opened and the odor was subjected to sensory evaluation according to the following evaluation criteria.
~Evaluation criteria~
○: Unpleasant odor is weak ×: Unpleasant odor is strong (2) Printing density The obtained ink is loaded into an inkjet printer (Orifice X9050, manufactured by Riso Kagaku Kogyo Co., Ltd.), and the paper type of the print setting is normal. The image density (OD value) of the front and back of a solid image printed on plain paper (ideal paper thin mouth, produced by Riso Kagaku Co., Ltd.) using paper and image quality as a standard (300 x 300 dpi) is an optical densitometer (RD920, Macbeth In addition, the OD value of the non-printed portion of the printed material was measured in the same manner, and the printing density of the solid image portion was evaluated according to the following evaluation criteria. A value ΔOD obtained by subtracting the OD value of the non-printed portion of the printed matter from the image density (OD value) was obtained and evaluated according to the following criteria: In the evaluation of show-through, the lower the image density on the back side, that is, ΔOD The smaller the value, the better.
~Evaluation criteria~
Print density (Table OD)
○: 1.05 or more Δ: 1.04 to 1.00
X: 0.99 or less printing density (back ΔOD)
○: 0.15 or less Δ: 0.16 to 0.20
X: 0.21 or more

From Table 2, all of the non-aqueous inks of Examples 1 to 5 had a weak odor, and the printing density evaluation on the front and back surfaces was good. Moreover, in Example 6, since the alkyl (meth) acrylate in which the carbon number of the alkyl group is outside the range of 8 to 18 is used, the printing density on the surface is slightly inferior, but is practically sufficient. .
On the other hand, in Comparative Examples 1-5, the favorable evaluation result was not obtained about either odor or printing density. Comparative Example 1 in which polyethyleneimine and the monomer (A) were not reacted and each was added individually was inferior in odor evaluation, and Comparative Example 2 in which polyethyleneimine was not added aggregated and could not be used as an ink. . Comparative Example 3 in which polyethyleneimine was further added as a pigment dispersant to the non-aqueous ink of Example 1 was inferior in odor evaluation. Further, Comparative Example 4 using only Solsperse 28000 as a pigment dispersant was inferior in evaluation of printing density, and Comparative Example 5 in which polyethyleneimine was further added to the non-aqueous ink of Comparative Example 4 was inferior in odor evaluation. .

Claims (4)

A non-aqueous ink containing at least a pigment, a pigment dispersant, and a non-aqueous solvent,
The pigment dispersing agent, beta-and containing at least the polymer as a constituent monomer (A) having a dicarbonyl group, a water-soluble resin having an amino group (B), at least comprises a copolymer as the component The
In the copolymer, the mass ratio ((A) :( B)) of the monomer (A) having the β-dicarbonyl group and the water-soluble resin (B) having the amino group is from 1: 2 to 20: 1,
Non-aqueous ink. The non-aqueous ink according to claim 1, wherein the copolymer contains an alkyl (meth) acrylate (C) having an alkyl group having 8 to 18 carbon atoms as a constituent component. at least comprising the polymer as a constituent monomer (A) having a β- dicarbonyl groups, a water-soluble resin having an amino group (B), Ri Do at least comprising a copolymer as the component,
In the copolymer, the mass ratio ((A) :( B)) of the monomer (A) having the β-dicarbonyl group and the water-soluble resin (B) having the amino group is from 1: 2 to 20: 1,
Pigment dispersant. A method for producing a non-aqueous ink comprising at least a pigment, a pigment dispersant, and a non-aqueous solvent,
A polymer containing at least a monomer (A) having a β-dicarbonyl group as a constituent component is synthesized, and then a copolymer containing at least the polymer and a water-soluble resin (B) having an amino group as constituent components is synthesized. And a step of preparing a pigment dispersant;
See containing said pigment dispersing agent, a pigment, a step of at least mixing and dispersing a non-aqueous solvent, and
In the copolymer, the mass ratio ((A) :( B)) of the monomer (A) having the β-dicarbonyl group and the water-soluble resin (B) having the amino group is from 1: 2 to 20: 1,
A method for producing a non-aqueous ink.